The present invention relates to a connecting apparatus for a lightning arrester mounted on a tower supporting overhead transmission lines.
It has been the usual practice in the past that an overhead transmission line including one or plurality of circuits is supported at one end of a suspension insulator (supporting insulator) attached at its other end to one arm of each steel tower, thereby forming a transmission system. In this type of transmission system, when lightning strikes the tower or the overhead ground wire or the overhead transmission line at the top of the tower, a short-circuit is established between the arcing horns provided at the ends of the supporting insulator thereby causing an instantaneous voltage drop and simultaneous grounding of the plurality of the circuits. Such voltage drop and simultaneous grounding cause an instaneous service interruption of the transmission system with the resulting great effect in a wide range of fields, e.g., electronic apparatus which have recently come into general use. Thus, with a view to preventing any effects due to a lightning strike on a transmission system, proposals have recently been made in which a lightning arrester employing a nonlinear resistor is arranged in parallel to a supporting insulator on each steel tower supporting an overhead transmission line. (See Japanese Unexamined Publications Nos. 60-5736 and 60-32267).
As mentioned above, the lightning arrester is arranged, along with the supporting insulator, on the steel tower and the lightning arrester is connected through a connecting conductor to the end of the supporting insulator at which the overhead transmission is fixed. In this case, the connecting conductor of a small wire-diameter is used in consideration of possible disconnection due to the melting of the connecting conductor. At this time, in the case of the ordinary direct ground system the single-line ground current is on the order of several hundreds amperes and therefore it is necessary to use the connecting conductor of 0.5 to 2 mm in diameter. However, this diameter results in an increased electric field and thus there is the danger of causing radio interference. On the contrary, if the connecting conductor of about 10 mm in diameter is used, disconnecting means is used to separate the lightning arrester from the supporting insulator as occasion demands.
When the connection provided by the connecting conductor between the lightning arrester and the supporting insulator is disconnected by the disconnecting means, the disconnected connecting conductor hangs down so that one end of the connecting conductor disconnected by the disconnecting means is caused by wind to swing to approach the changed portion of the supporting insulator and there is the possibility of this approach causing a reflashover.